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Glossary term: Color Index

Description: The color index of a star or other celestial object is the difference between its brightness or magnitude, as measured in two different color or wavelength bands, such as yellow and blue. The most common color index is (B-V), where B is the magnitude as measured through a standard blue filter, and V is the magnitude as measured through a standard yellow filter. The B filter is similar to the color sensitivity of old-fashioned photographic plates, and the V filter is similar to the color sensitivity of the human eye. For stars, (B-V) is a measure of the temperature, though it can also be affected by the reddening effect of dust between the stars.

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Term and definition status: This term and its definition is still awaiting approval

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".